Hard disc drives (HDDs) typically comprise one or more magnetic media discs or other magnetic storage media, each having concentric data tracks for storing data. Where multiple discs are used, a stack is formed of co-axial discs having generally the same diameter. A transducing head carried by a slider is used to read from and write to a data track on a given disc. The slider is carried by a head arm assembly (HAA) that includes an actuator arm and a suspension assembly, which can include a load beam and a gimbal. The gimbal can be a separate metallic element secured to the load beam to support the slider thereon, or can be integrally formed with the load beam. During operation, as an associated disc spins, the slider glides above the surface of the disc on a small cushion of air. The actuator arm pivots to movably position the slider with respect to the disc. A microactuator assembly can be included to provide additional precision positioning of the suspension assembly and the slider. Electrical connections extend along the suspension to electrically connect the transducing head to components located at or near the actuator arm. Those electrical connections can be formed on the suspension itself, or can be located on a separate interconnect structure supported relative to the suspension, such as a flex-on suspension (FOS).
Magnetic storage media can store data as bits with magnetization directions in-plane, or perpendicular to a plane of the media. Greater storage densities can generally be achieved with perpendicular recording.
The slider includes a slider body and an overcoat that includes the transducing head. The overcoat is electrically insulative. A plurality of bond pads are formed on the slider, such as at a trailing edge or top surface of the slider, for electrically connecting elements of the transducing head to external circuitry through the overcoat.
The transducing head typically includes a writer and a reader. The reader includes a sensor for retrieving magnetically encoded information stored on the disc (or other magnetic storage medium). Magnetic flux from the surface of the disc causes rotation of a magnetization vector of a sensing layer or layers of the sensor, which in turn causes a change in the electrical properties of the sensor that can be detected by passing a current through the sensor and measuring a voltage across the sensor. Depending on the geometry of the sensor, the sense current may be passed in the plane (CIP) of the layers of the sensor or perpendicular to the plane (CPP) of the layers of the sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary to recover information encoded on the disc.
The writer, for a perpendicular recording transducing head, typically includes a main pole and a return pole, which are separated from each other at an air bearing surface (ABS) of the transducing head by a gap layer. The return pole can include a front shield (or trailing shield) portion that extends along the ABS. A use of a front shield can offer an improved magnetic field gradient to the writer for improved linear recording density. The main pole and return pole can be connected to each other at a region distal from the ABS by a back gap closer or back via. One or more layers of conductive coils are positioned between the main and return poles, and are encapsulated by electrically insulating layers. The conductive coils can have different configurations, such as helical and pancake configurations. To write data to the disc (or other magnetic storage medium), an electric current is applied to the conductive coils to generate a magnetic field in the disc under a pole tip of the main pole. By reversing the direction of the current through the coils, the polarity of the data written to the magnetic storage medium is reversed, and a magnetic transition is written between two adjacent bits of the magnetic storage medium.
Advances in magnetic recording head technology are driven primarily by a requirement for increased recording density in HDDs. As recording density increases, track widths of data tracks of the magnetic storage media tend to become smaller, that is, track pitch increases. The performance of modern perpendicular magnetic recording heads is related to the magnetic write fields that can be supplied to write to the perpendicular medium, which tends to be reduced when track pitch is relatively high. Configuration of the components of the transducing head can affect performance, with respect to the write fields that can be generated. For instance, relatively high track pitch tends to limit the size of the pole tip of the writer, specifically the pole tip width and reduces the size of the gap layer between the main pole and the front shield (as well as between the main pole and the return pole). Both of those factors tend to weaken the performance of the writer. The presence of the front shield also tends to weaken the performance of the writer in terms of the magnitude of magnetic fields the writer can produce.